1x 1000 watt rear drive VS 2x500watt all wheel drive

[Vanart]

Say there is the same bike, same rider and same battery ( 48 w 15 AH) but one version of the bike has 48 v 1000W rear drive gear less motor and the other version has two motors installed but only 48 v 500w
one thing is more or less clear that they will draw the same amount of power from the battery.

The big question is how do they compare in speed / distance and torque?

Thank you for any info

VS

 

[dogman dan]

Using the example in the picture, you have one 1000w motor vs two 1000w motors. Actually, either can be run at 200w- 1500w with no problems at all.

The two 1000w motors run on 500w each would of course cost twice as much and be twice as heavy as one motor run at 1000w.

The double motor advantage comes when you want 3000w up steep hills. The same motor pulling 3000w is a bit too much to last long before damaging heat builds up. So two motors, each running only 1500w works very good then.

So does one motor, one big one able to take 5000w.

But that's the motors you show. If you were to use the very small motors, say 250w types, then double motors might be worth it. But I can't see why you'd do that, when the 28mm magnet dd motors able to take 1500w are so dang cheap. 1000w rarely fazes them, unless you climb stupid steep hills with one. Up to 10% grades, they do just fine on 1200w, 48v with a 20 amps controller.

As for the speed, distance, torque question, that all depends on what the real world wattage you are using, and how fast you ride.

But, I tested several different types of motors, both geared and not geared. If you ride 20 mph, all used about 400w. At 400w, you get the same distance from all the motors. At 20mph none of the motors were in their inefficient rpm, so even different windings matter little for cruising at 20 mph. 400w for one hour is 400wh. It doesn't matter what motor, if you ride at 400w, you get about 20 mph, and in one hour with no stops you will go 20 miles using 400wh.

In the real world of course, you rarely go 20 miles non stop at 20 mph, and never have a hill, or any wind. So it varies day by day, and range differs on different routes. But in general, one hubmotor vs two would still use about 400w to go 20 mph.

 

[John in CR]

Hubmotors are power limited by the heat they can dissipate. That means 2 motors of the same efficiency and external surface area can be run at double the power of 1 regardless of the power rating. If you run at significant power, then the dual motor rig will be more efficient overall too when run at the same power. Some of that will come from running cooler and some from each motor being run at essentially half the load. At modest power the 2nd motor is closer to break even or a bit lower. FWIW, the guys running 2wd all swear by it.

 

[dogman dan]

You always say it better than I do.

I just wanted to say, no need to have two motors of the type in the pictures to run 1000w. If I couldn't melt one climbing the rocky mountains in my climate, nobody else will.

But that's on roads limited to about 10% grade, and limiting the wattage to 1200w. Above that grade, you can melt them easy, so for that, or for hauling a fully loaded cargo bike up regular hills, two motors would have each motor running cooler. For 3000w, and that type of motor in the picture, two motors for the win.

I was on my way to putting two motors on my monster of a cargo bike, but then I got my hands on a good large motor, one able to do 3000w with no problems.

 

[d8veh]

I've built three two-wheel drives. I'm surprised that more people don't do it. I reckon that a 250w front motor and a 500w geared motor in the rear will give equivalent power to a single 1000w DD motor. You need to match the winding speeds of the two motors. The lighter the motor on the front, the better handling your bike becomes and the less chance of damaging your forks.

My experiments show that two motors don't use more power than a single motor. They're about the same overall, but if you do a lot of climbing, two motors will be more efficient because you can use less throttle to increase efficiency.

 

[dogman dan]

Though I never did the experiment, I believe you are correct. Two smaller motors to get to 1000w has some very good points, particularly less motor heating if you run them hard hauling cargo or climbing steep hills.

2 wheel traction in corners is great, as long as the front motor is not pulling more than 1500w. So that's one reason to do the two motors. Another might be you already have one of the small motors. Another small one might be cheaper than a new large one. Or, like I was thinking on my longtail, two motors could give you redundancy you would like to have on a very long tour.

Lots of good reasons for two motors. I was just scoffing the idea of the motors in the pictures needing two of them to get to 1000w. One of those typical 28mm dd motors can do a lot, and running them at 1000w rarely melts one. Never melts one if the grades are not above 8% and the weight is "normal".

Two of those 28mm dd motors to get to 3000w, that's a very good idea.

 

[Vanart]

Thank you,
Though the pics where just to give an idea...
I wander if i could just connect to the same controller the second motor so that i have "all wheel drive" bike.Obviously the controller will not have a separate sets of wires for the both wheels so I would have to just split the motor output to 2 motors.

Puzzled in Vancouver,

 

[dominator]

I'm starting a new bike build and have been considering this same question, they currently dont have the 1000w version of the motor that I want only the 750w which is about 13lbs, I could buy 2 500w motors though that weigh 10lbs each, the main concern I have is

(1) 750 w motor is rated at 35+ mph

(1) 500 w motor is rated at 28+ mph

Will (2) 500 w motors be faster than (1) 750 w motor?

 

[dogman dan]

You need two controllers for two brushless motors. You can't keep two motors in synch.

Re the next question. the fastest rated motor will be the fastest. So two slow motors will never be faster than one fast motor. The voltage and the winding combine to determine the maximum rpm, at no load.

But there is a possibility of two slow motors being faster, that would be the case if the fast motor was not given enough voltage, or wattage, to develop it's full potential. But that never happens since 20 amps is enough to get motors to max cruise rpm, so..... It would only be possible if the fast motor was given an incredibly weak controller.

Just to nitpick, your question is theoretical? 750w won't make a normal bike go 35 mph on the flat, unless you have a 35 mph tailwind. It takes 1500w to go 35 mph. So if you took that fast motor, and gave it 36v at 20 amps, or 48v at 15 amps, you'd still never reach 35 mph. But 48v at 15 amps would be fastest.

 

[dominator]

No my question is not theoretical in that sense the motor im talking about is the falco hx750 rated at 35+ mph if you purchase the off road module, they have a you tube video of a wheel spinning with no load on 36v hitting 177 kph and on 48v hitting 212kph not sure how legit it is though but yea until the store lets me demo one im hesitant about their claims. The bike i bought last night was a 16" frame and just found out the triangle battery i wanted from falconev needs a 19" frame min im at a cross road now on what to do, also falco motors the controller is built into the motor and their wireless command unit can control two motors and synch them which they confirmed with me which is why I was considering awd but if two small motors cant beat one faster motor i wont be interested.

 

[999zip999]

Vanart what are you looking for a hill climbing bike or more speed on the flats and or offroad ? The price of the Falco motor setup and it's 5 phase wireless controller and triing to find replacement parts at a reasonable price. Could be the deal killer. They look well made. Then you can run two motors one controller ? ?

 

[Vanart]

I live in a city with no almost no winds and we have no hills. So I was hoping to give a little jump start to my tandem. I am putting afront wheel motor on this bike:
http://endless-sphere.com/forums/viewtopic.php?f=3&t=52795
I decided to go 48v 500W . It is a second bike that I am building and the first one had 1000W version of the same motor and it has a very smooth start. so I am hoping that 500 will not kill my front fork. I am also installing the torque arm to give additional protection.
I am not looking for a speed (though that 1000 w version is giving me 45-55 km per h on 700 wheel) nor i want torque. Just a little excitement in a case I don't want to pedal.
where is this falko deal you are referring to?

 

[dominator]

I'll probably be getting the falco system mid week this week after my new bike is assembled by the bike shop. Already wasted 2.1k on the motiv and now selling it at a 70% loss.... Really hoping this falco motor doesn't fail me, not much info on it either guess it is fairly new. I'll be happy honestly if I can get 30mph, originally I was going to convert my motiv bike to take the new motor and use my existing 48v 10ah battery from the motiv but now I'll be downgrading to a 36v 11ah water bottle battery that comes with the falco systems, hopefully it outperforms my motiv, otherwise its gonna be more money wasted, but at least this bike will fit me, the motiv was a little large for me.